The present invention relates to a thrust reverser for a turbofan-type jet engine, more particularly such a system incorporating a thrust reverser door having a gas flow deflector.
Turbojet engines of the turbofan-type are well known in the art and typically comprise a primary exhaust gas duct to exhaust the high temperature gases after passing over the stages of the turbine. Turbofan-type engines also include a secondary duct concentrically located about the primary exhaust gas duct so as to define a annular space therebetween. Large diameter turbofans, typically mounted on the front of the jet engine, direct air through this annular space to increase the performance characteristics of the engine.
Thrust reversers are also well known in the art and usually comprise one or more thrust reverser doors serving to redirect the flow of gases from their normal upstream to downstream direction to a direction which has a component in the forward direction In civilian aircraft applications, where such engines have a relatively high bypass ratio (i.e. the ratio of the quantity of gases passing through the secondary or cold flow annular space to the quantity of gases passing through the primary duct), the thrust reverser may be applied solely to the secondary or cold flow duct. In that instance, the thrust reverser door and the actuating mechanism are usually integrated into the wall of the secondary duct.
In such known systems, the thrust reversing doors are displaceable between a retracted position, in which they form a part of the outer wall of the secondary duct and do not impede the air flow through the annular space, and an extended position in which the door will block at least a portion of the air flowing through the annular space and re-direct it in a direction having a forward acting component.
Thrust reversing doors may assume various shapes, from the semi-shell curved door noted in French Patent No. 2,490,731 to a plurality of flap-type structures illustrated in U.S. Pat. Nos. 4,410,152 to Kennedy et al. and 4,485,970 to Fournier et al.; and French Patent No. 2,559,838.
In the latter instance where a flap-type door is utilized, a deflector will usually be attached to the upstream edge of the door so as to redirect the gas flow to have a more forward acting component. In order to provide for adequate performance of the thrust reverser, this deflector must have a minimum length extending inwardly from the inner surface of the thrust reverser door. In order to accommodate this length when the door is in a retracted or normal thrust position, the inner wall of the secondary duct usually is located adjacent to the end of the deflector in order to prevent the deflector from extending into the annular air space and disrupting the air flow.
However, in order to maximize the performance of the thrust reverser, the inner surface of the door usually defines a cavity or a concave portion. When the door is in its retracted position, this concavity is located downstream of the deflector. The presence of this concavity when the thrust reverser door is in the retracted position produces aerodynamic losses in the air flow passing through the annular space of the secondary duct, thereby reducing the efficiency of the engine when in the normal thrust mode